Variation of Chemical Compositions and Fatty Acids Profiles of Chlorella sp. Utilizing Physical Shocks

Chlorella has various industrial applications; therefore, optimizing its induced physical shock conditions is very important. This study aimed to evaluate the effect of different environmental shocks on the nutrients concentration in Chlorella sp. The algae were cultivated until stationary phase (12 days) using a Guillard medium followed by exposure to seven different shock conditions including salinity, pH and starvation for six days. The photoperiod throughout the experiment was set to 12L:12D condition. The samples were harvested on days 15 and 18 at the end of dark and light periods. The results revealed that protein content declined significantly in all treatments from about 38% to less than 18% through day 12 to day 18, whereas the lipid content increased significantly in all treatments compared to control. The starved algae (T4) with 41.53% and those starved at high pH (T5) with 56.60% had significantly higher lipid than control and other treatments in dark and light periods on day 18, respectively. Carbohydrate content decreased in most of the shock treatments, but ash level increased under salinity shock compared to control. Significantly higher level of total PUFA (45.12%) was detected in algae exposed to pH, salinity and starvation shocks (T2) in light period on day 18 compared to control. Highest percentage of arachidonic acid was detected in treatment five (2.18% on day 15 and 2.03% on day 18) and value of DHA was highest in treatment seven (5.37% on day 15 and 5.02% on day 18) at the end of the light period compared to all treatments. Significantly higher linoleic acid (32.31%) was detected at high salinity shock at the end of light period on day 18, whereas highest levels of alpha linolenic acid (similar to 13%) was found in algae under the influence of pH, salinity and starvation in both dark and light periods compared to control. It is concluded that combination of environmental shocks especially pH and starvation can induce biosynthesis of lipids and fatty acids in Chlorella sp.